Decreased bone strength in older men with type 2 diabetes mellitus

Observational cohort studies have found that type 2 diabetes mellitus is associated with a 50% to 80% increased risk of hip fracture, as well as a 30% to 70% increased risk of fracture of the proximal humerus and foot.
Although there is awareness of the higher fracture rates among diabetic adults, there are few data available on the factors responsible for this increased risk. Identifying these factors is a critical step in the development of potential interventions to prevent fractures among the growing segment of the adult population with type 2 diabetes mellitus.

The effects of type 2 diabetes mellitus on bone volumetric density, bone geometry, and estimates of bone strength are not well established. The authors of a recent study [1] used peripheral quantitative computed tomography to compare tibial and radial bone volumetric density, total and cortical bone area and estimates of bone compressive and bending strength in a subset (=1171) of men (>65 years of age) who participated in the multisite Osteoporotic Fractures in Men (MrOS) study. Analysis of covariance–adjusted bone data for clinic site, age, and limb length and further adjusted for body weight were used to compare data between participants with and without type 2 diabetes mellitus.

At both the distal tibia and radius, patients with type 2 diabetes mellitus had significantly greater bone volumetric density and a smaller bone area. The higher bone volumetric density compensated for lower bone area, resulting in no differences in estimated compressive bone strength at the distal trabecular bone regions. At the mostly cortical bone midshaft sites of the radius and tibia, men with type 2 diabetes mellitus had lower total bone area, resulting in lower bone bending strength at both sites after adjusting for body weight despite the lack of difference in cortical bone mineral density at these sites.

These data demonstrate that older men with type 2 diabetes mellitus have bone strength that is low relative to body weight at the cortical-rich midshaft of the radius despite no difference in cortical bone mineral density.

1. Petit MA et al. J Bone Miner Res. 2010;25: 285-291.